The former Kate Middleton opted for a pale blue Emilia Wickstead coatdress with a matching blue belt. She paired the look with pointed nude pumps and delicate jewelry — because let's be honest: This coat deserves to be the star.

The duchess started the day with a visit to the Grand Duke Jean Museum of Modern Art before viewing a sizable cycling-themed cake topped with trees, riders on their bikes, and tiny pastries!

This cake's almost taller than the duchess! Jeff Spicer / Getty Images

But even that delicious mountain of cake couldn't distract us from her show-stopping coatdress.

The powder-blue frock is very similar in color to the blue Ralph Lauren dress and jacket worn by first lady Melania Trump for for her husband's inauguration in January. It's even similar to the baby blue coat first lady Jacqueline Kennedy wore for her husband's inauguration in 1961!

From the '60s to now, this look is classic!Getty Images; AP

It appears there's at least one key lesson to take away from these stylish women: Blue is best!